The present invention is directed to a method for preparing reactive metal surfaces, particularly uranium surfaces, whereby the metal is immediately reactive to hydrogen gas at room temperature and low pressure.
Processes for preparing metal compounds usually require specific heat and pressure conditions. It is, however, sometimes desirable to prepare metal compounds without these conditions. This situation might arise in the pyrotechnics industry where it is desired to pack the body of a flare with as much metal hydride as possible. Preparation of the metal hydride powder may be a time-consuming process requiring weighing and packing of the metal powder into the flare. The packing procedure requiring the use of a piston may also be undesirable because the pressure of the piston may deform or split the body of the flare. Moreover, many metal hydrides are pyrophoric and cannot be safely compressed because of the explosive danger presented by accidental sparks, and metal hydrides generally lose hydrogen upon heating so that heating during the process could present the possibility of a hydrogen explosion. Heating may also deform the carefully machined parts.
In addition, most metal hydrides are very reactive and cannot be handled in air or moisture without the risk of fire or the danger of ruining the hydride by oxygen contamination. Thus it is desirable for many reasons to be able to prepare metal hydrides and other metal compounds in situ without heat, undue pressure, excessive handling, or long waiting periods.
With relation to another field of industry, rapid advances in the electronics field often require the preparation of a compound on the surface of a metal in a very specific configuration, such as in a figure 8, an "X", or more complicated designs. Sometimes this is possible by procedures known in the art of alloy and semiconductor preparation. However, when the desired compound to be formed is a hydride, the known techniques have been found to be unsatisfactory.
The preparation of uranium hydride is one important process wherein previous procedures have been found to be unsatisfactory. Uranium metal, as most metals, naturally has an adherent oxide coating. The oxide layer is believed to slow the penetration of hydrogen molecules to the metal surface, thereby inhibiting the hydrogen-uranium reaction. This slow penetration of the hydrogen molecules creates an "induction period" or delay period of the reaction which is usually of an unpredictable length but may vary from a few minutes to several hours. Once initial penetration of the hydrogen molecules has taken place, the hydrogen-uranium reaction may then begin. However, the delay or the "induction period" is an undesirable characteristic.